Large optical Stark shifts in single quantum dots coupled to core-shell GaAs/AlGaAs nanowires.

Nanowire quantum dots (NW-QDs) can be used for future compact and efficient optoelectronic devices. Many efforts have been made to control the QD states by inserting the QDs in doped structures and applying an electric field in a nanowire system. In this paper, we use down-conversion and up-conversion photoluminescence excitations to explore the optical and electronic properties of single quantum dots in GaAs/AlGaAs core-shell nanowires. We investigate a large optical Stark shift in this system as a new method to tune the QD states. When the tunable laser lies within the spectral bandwidth of ZB/WZ GaAs (780 nm-860 nm), we observe an extremely large optical Stark shift of 1.3 nm (0.5 nm) with increasing excitation power at a resonant wavelength of 800 nm (840 nm) in GaAs states. The ability to in situ control the energy states of self-catalyzed NW-QDs should open a new way for quantum light sources and nonlinear optics in a nanowire system.